Field of the Invention
The invention generally relates to the handling of service request procedures, and more particularly, to methods for handling service request procedures, and apparatuses using the same.
Description of the Related Art
In a typical mobile communication environment, User Equipment (UE), such as a mobile phone, smartphone, laptop computer, or panel Personal Computer (PC), etc., may communicate voice and/or data signals with one or more service networks. The wireless communications between the UE and the service network(s) may be in compliance with various Radio Access Technologies (RATs), including the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA 2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, LTE-Advanced (LTE-A) technology, or Time Division-LTE (TD-LTE) technology, and others.
Taking the WCDMA/LTE technology in compliance with the 3GPP TS 24.301 specification, v12.4.0 (referred to herein as the TS 24.301 specification) and the 3GPP TS 24.008 specification, v12.7.0 (referred to herein as the TS 24.008 specification) as an example, a UE has to start a back-off timer when a service request procedure has failed for a maximum number of retries, wherein the back-off timer refrains the UE from initiating the service request procedure till it expires. The design of the back-off timer is to grant the service network sufficient time for recovering from temporary problems. However, when the back-off timer is running, not only is it not allowed to initiate the service request procedure for a normal service, but it's also not allowed to initiate the service request procedure for an emergency bearer service. As a result, the UE will be delayed in obtaining an emergency bearer service.
In addition, the start of the back-off timer may imply that a particular node (e.g., the Mobility Management Entity (MME)) of the service network is facing some sort of problem and temporarily cannot process the UE's service requests. However, the UE remains forbidden from initiating the service request procedure even when it has successfully registered with another Routing Area (RA), Tracking Area (TA), or Public Land Mobile Network (PLMN), or even when it has switched to use another Radio Access Technology (RAT), which implies that the UE has changed to register with another node of the same service network or with another service network. As a result, the UE cannot obtain either a normal service or an emergency bearer service as it should in the newly registered area or network.